Code Quality

Software Design

Reducing complexity through thoughtful software design

Reduce software complexity using John Ousterhout's philosophy of deep modules, information hiding, and strategic programming. This skill helps your AI agent design interfaces that are simple on the outside and powerful on the inside.

A Philosophy of Software Design by John Ousterhout

A Philosophy of Software Design

by John Ousterhout

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Install this skill
npx skills add wondelai/skills/software-design-philosophy --global

This skill is compatible with Claude, Claude Code, Claude Cowork, Codex, Cursor, OpenClaw, Hermes Agent, and other agentskills.io-compatible agents.

Key Concepts

What your agent learns

Deep vs Shallow Modules

The best modules have simple interfaces that hide significant implementation complexity — depth matters more than number of modules.

Information Hiding

Each module should encapsulate design decisions that are likely to change, exposing only what callers need to know.

Strategic vs Tactical Programming

Invest time to design clean abstractions upfront (strategic) rather than hacking quick fixes (tactical).

Define Errors Out of Existence

Design interfaces so that error conditions cannot occur, rather than handling them after the fact.

Complexity Signals

Watch for change amplification, cognitive load, and unknown unknowns — the three manifestations of complexity.

About the Author

John Ousterhout

Stanford professor, creator of Tcl/Tk, ACM Software System Award winner

John Ousterhout is a professor at Stanford University and the creator of Tcl/Tk, the Raft consensus algorithm (co-creator), and the RAMCloud storage system. He has been awarded the ACM Software System Award and the UC Berkeley Distinguished Teaching Award.

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Example Prompts

Try these with the skill installed

Evaluate whether these modules are deep or shallow and suggest improvements using software-design-philosophy skill

Design review

Redesign this API to hide implementation complexity behind a simpler interface using software-design-philosophy skill

API design

Identify complexity signals in this codebase and propose fixes using software-design-philosophy skill

Code review

Refactor this error handling to define errors out of existence using software-design-philosophy skill

Error handling
Related Skills

More in Code Quality

Clean Code
Writing readable, maintainable code
Clean Code — Robert C. Martin
Pragmatic Programmer
Practical software craftsmanship
The Pragmatic Programmer — Andrew Hunt & David Thomas
Refactoring
Improving code design through systematic refactoring
Refactoring — Martin Fowler
Legacy Code
Safely change untested code: seams and characterization tests
Working Effectively with Legacy Code — Michael C. Feathers
Put it to work

Guides that use this skill

Create · App

How to Create a New App with AI Skills

Read guide Improve · App

How to Improve an Existing App with AI Skills

Read guide Deep dive · Engineering

From Vibe-Coded Prototype to Production-Ready Product

Read guide Deep dive · Engineering

How to Refactor a Codebase Buried in Technical Debt

Read guide Deep dive · Architecture

How to Design the Best Possible Architecture for a New App

Read guide

Install Software Design

Free, open-source, and ready in 30 seconds.

npx skills add wondelai/skills/software-design-philosophy --global
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MIT Licensed · Works with Claude, Claude Code, Claude Cowork, Codex, Cursor, OpenClaw, Hermes Agent & other agentskills.io agents · No account needed

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